In making movies on location it is necessary to transport a great deal of special equipment. Much of this equipment is used for lighting purposes. When the shooting of a scene commences, a large number of lights must be turned on more or less instantaneously. When the shooting is interrupted for more than a very brief time the lights are turned off.
Continuous operation of the lights would involve an excessive expense. It would also subject the actors and actresses and work crews to unnecessary eyestrain. Furthermore, the continuous burning of the lights could produce excessive heat, which would be undesirable for many reasons.
In order to control lighting for this purpose it is necessary to have switching units that can be transported to the particular movie location. The switching equipment must have high electrical capacity, be easily controlled, and be safe to use by the operating crews.